1. Field of the Invention
The present invention relates to a rotary grinding machine and a fine adjustment of the depth of cut thereof. More particularly, the present invention relates to a rotary grinding machine in which a work table carrying a workpiece to be ground rotates relative to a grinding wheel.
2. Description of the Related Art
In a typical rotary grinding machine, there is a difference in peripheral speed between a central portion and a circumferential portion of the work table. Because of this difference in the peripheral speed, the surface of the workpiece to be ground is not always even after the grinding operation is finished. Namely, a close look at the surface of the workpiece which has been ground will reveal that the portion of the surface located near the center of the workpiece has been cut deeper than the portion of the surface located adjacent to the periphery of the workpiece. To eliminate this unevenness of the ground surface of the workpiece, usually a predetermined relative inclination is provided between the surface of the workpiece and the surface of the grinding wheel, in accordance with the scope of the unevenness. This inclination depends on the machinability, size, or cutting conditions of the workpiece, and accordingly, must be adjusted to match those conditions. The adjustment of the inclination is usually carried out by changing the inclination angle of the grinding wheel with respect to the workpiece.
Adjustment of the inclination angle of the grinding wheel per se is usually effected by the use of adjusting washers or plates which can be located at one side of the bottom surface of a column holding the grinding wheel, so that the column is inclined. The angle of inclination depends on the number of the adjusting washers used. However, in this conventional adjustment, it is very difficult to finely adjust the inclination angle, since the adjustment of the inclination angle is usually in the order of microns. In addition, according to the conventional method of adjusting the inclination of the grinding wheel, another disadvantage arises in that the column, which is secured to a base (bed), tends suffer from an irregular and unbalanced securing load from fixtures, such as bolts, used to secure the column to the base, since the adjusting washers are provided between the bottom of the column and the base to incline the column, and accordingly, the grinding wheel, as mentioned before. This unbalance in the securing load results in a lack of stability of the column, and accordingly, the grinding wheel, and in a lessening of the required strength of the connection between the column and the base.
Furthermore, it is very difficult to finely adjust the depth of cut of the grinding wheel in the order of microns by the conventional method, since this fine adjustment can be made only by adjusting the height of the grinding wheel by moving it up and down.